Vehicles are capable of towing along a variety of trailers and/or cargo. Vehicle powertrain control units are configured to optimize vehicle performance at a pre-defined operating mass. Consequently, vehicle operations may need to be modified upon addition of a trailer and/or cargo to the vehicle. In one example, vehicles may be equipped with a specialized operating mode wherein vehicle operation is optimized for towing operations. The operating mode may be selected automatically or based on operator input. However in order to improve vehicle performance during towing, the size, weight and other characteristics of the trailer that is being towed may need to be input to the vehicle controller.
Accordingly, various approaches have been developed to detect a trailer and/or cargo coupled to a vehicle. One example approach shown by Hessmert et al. in U.S. Pat. No. 6,655,222 discloses a method to determine a trailer load attached to a vehicle based on an estimation of a current road gradient. Therein, wheel contact forces are used to estimate the current road gradient and total vehicle system mass. If a trailer and/or cargo is coupled to the vehicle, the total vehicle system mass is expected to be higher than the standard mass of the vehicle itself. The difference in mass may be used by the vehicle controller to detect the presence of a trailer and/or cargo coupled to the vehicle as well as to determine the mass of the attached trailer and/or cargo.
However, the inventors herein have recognized potential disadvantages with the above approaches. As one example, they may be unable to effectively characterize the size and in particular the size and optionally the shape of frontal area of the trailer. As such, for a trailer of a given mass, based on the size of the frontal area, wheel contact forces may change. The wheel contact forces may further change based on the vehicle speed and instantaneous road conditions (which may be different from the average road conditions). In the absence of accurate estimation of trailer characteristics, the vehicle may have to switch gears frequently causing shuffles, delays and trouble while accelerating, thereby impacting the driving experience. Also, operating a vehicle with a higher than expected weight without significant adjustments to powertrain operations may lead to increased fuel consumption and a high level of stress on powertrain components, leading to warranty issues. Vehicle stability and control may also be affected by operating the vehicle without compensating for the additional towing load.
The inventors herein have identified an approach by which the issues described above may be at least partly addressed. One example method includes during vehicle driving over a road segment, inferring characteristics of a trailer attached to a vehicle based on a real-time road gradient relative to an expected road gradient for the road segment; and adjusting vehicle operations based on the inferred characteristics. In this way, trailer characteristics may be reliably determined and engine operation adjusted accordingly.
As an example, a vehicle control system may automatically detect the presence and details of a trailer and/or cargo attached to a vehicle during vehicle travel based on a real-time estimate of a road gradient. A controller may estimate the gradient of the road on which the vehicle is travelling in real-time based on an estimated wheel force. Wheel forces may be estimated during different driving conditions such as during acceleration, deceleration, and steady-state vehicle speeds, and on road segments having variations in elevation. The real-time estimated road gradient is then compared to an externally sourced road gradient estimate, such as one retrieved from an off-board map via a navigation system of the vehicle. As such the real-time road gradient as estimated based on wheel forces may be influenced by the size (dimension and volume of trailer), weight (mass of trailer), and size (dimension and volume) of a frontal area of a trailer coupled to the vehicle. Based on a difference between the real-time estimated road gradient and the externally sourced road gradient, the controller may determine if a trailer is being towed by the vehicle, and further determine trailer characteristics such as trailer size, weight and size of frontal area. In particular, a difference between the wheel forces in the real-time estimate and the externally sourced estimate may be attributed to an additional load being towed by the vehicle. For example, based on the comparison, the controller may determine if the trailer is heavy or light, and further determine if the trailer has a larger or a smaller frontal area. In one example, the classification of the attached trailer may be carried out automatically without the requirement of any input from the user. Based on the determined trailer characteristics, engine operating parameters of the vehicle may be adjusted to improve vehicle performance. For example, a transmission gear shift schedule and fuel usage may be adjusted. Optionally, in the event that an off-board map is not available, an on-board map for a frequently travelled road segment may also be generated based on the real-time gradient estimate, and used during future travel on the given road segment.
In this way, by comparing a measured (real-time) road gradient to an expected externally-sourced road gradient, it may be possible to not only determine the presence of a trailer but also estimate trailer characteristics including its size, weight, and size of frontal area. The comparison enables difference in wheel forces between the measured estimate and expected estimate to be correlated with specific trailer characteristics such as the presence of a small or large frontal area. By reliably determining trailer characteristics (including details of weight, size, and size of frontal area of the trailer) during vehicle travel, engine performance may be optimized for the specific kind of trailer, thereby improving operator driving experience, drivetrain temperature management, and fuel efficiency. The technical effect of creating and updating an on-board map with road gradient information is that even in the absence of an off-board map, such as due to lack of wireless connectivity and/or navigation data, the on-board map may be effectively used for determination of trailer characteristics.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.